Flashcards in Local Anesthetics Deck (31):
-cause more hypersensitivity reactions
-only 1 letter "i"
Ester durations and potency
Short: Procaine (1)
Long: Tetracaine (16)
Topical/Surface: Benzocaine, cocaine (2)
-2 letter "i"s
Amides duration and potency
medium: lidocaine (4), mepivacaine (2)
Long: bupivacaine (16), ropivacaine (16)
Esters: Onset and duration
duration: 25 min to 1 hour
onset: <15 min
duration: 2-3 hours
Amides: onset and duration
onset: 3-5 min
onset: 5 min
duration: 2-4 hrs
duration: 30min - 1hr
Local anesthesia MOA
block voltage-dependent sodium channels of excitable membrane from sending sensory info to the CNS
Which form of local anesthetic is better/faster at crossing the lipid membrane to reach the cytoplasm receptor site?
Which form of local anesthetic is the more effective blocking entity once inside the axon?
What effect does sodim bicarbonate have when added to a local anesthetic?
1. Accelerates the onset of action
2. Decreases burning sensation
What effect does adding epinephrine (alpha agonist sympathomimetic vasoconstrictor) to a local anesthetic?
(long acting don't need this - bupivicaine, ropivicaine, tetracaine and neither do topical local anesthetics)
What is the difference in esters and amides when it comes to metabolism?
Esters - metabolized in the blood by plasma cholinesterases (very rapid)
Amides -metabolized by liver (so, higher risk of liver toxicity with liver dysfunction)
What type of fiber would be most easily blocked?
a small myelinated fiber
What type of fiber would be most difficult to block?
a large unmyelinated fiber
Which type of fiber is hardest to block?
Type A - Alpha (proprioception, motor)
Which type of fiber is easiest to block?
Types B, C and Type A - delta (pain, temperature)
Which would be blocked first a medium myelinated fiber or a small unmyelinated fiber?
the myelinated fiber
-Largest fiber type
-Second largest fiber
-3rd largest fiber
-pain and temperature
-pain, temperature, itch
Sequence of nerves to be blocked
4. Light touch
-local anesthetic extradurally
-epidural block in the caudal canal via the sacral hiatus
injection into cerebrospinal fluid in the subarachnoid space
Why is bupivacaine banned by the FDA in obstetrics for epidural anesthesia?
How can you tell local anesthetics with and without epinephrine by the label on the bottle?
red label if it contains epi
Amides local anesthetics
Pharmacokinetics: hepatic metabolism
-bupivacaine is most likely to cause heart problems
-CNS effects (light headed, sedation, restlessness, nystagmus, tonic-clonic convulsions
Ester local anesthetics
Pharmacokinetics: rapid metabolism by plasma esterases
-Metabolites can cause antibody formation
ex. Benzocaine, cocaine, procaine, tetracaine
can convert hemoglobin to methemoglobin